Giant robots (vs|with|made from) Cthulhoid horrors!
In the 2020s, a series of brilliant (and then insane) scientists develop non-Euclidian geometry into an inexhaustible power source and incidentally antigravity. Since this is magic-based, vehicles powered by D-engines give bonuses to pilots who are roughly the same shape as the vehicle. It's as good an excuse for giant humanoid mecha as any, I suppose.
A few years later, a few billion aliens calling themselves the Nazzadi show up and announce that Earth is next in their scheme of galactic conquest. The tech levels are pretty close, so the war drags on for years, until one of the most senior Nazzadi spills the beans: the Nazzadi are really lightly-tweaked humans, cloned up and given a fake history by the migou lurking in their icy lairs on Pluto. Most of the Nazzadi switch sides and ally with their fellow humans against the inevitable migou attack.
Inevitably, the migou attack, this time piloting the warships and mecha themselves, because primates can't be trusted to do anything right. They take over much of the high-latitude regions of Earth, but humanity is able to mount enough resistance to avoid being immediately swept away.
While this is going on, three different cults (Nyarlathotep, Hastur, and Cthulhu) are busy trying to variously enslave, exterminate, or interbreed with humans, to make the world fit for their Old One masters, using superpowered agents made by merging humans and extradimensional horrors, Deep Ones and hybrids, or super-size servings of brutality. None of the cults or the migou have compatible goals, though, so although humanity is fighting a war on four fronts, so are all of its enemies. This may or may not help.
The system has a wacky dice mechanic: for skill rolls, you can take the highest number showing on any die, the sum of any matched sets (pair, three of a kind, etc), or the sum of any straight of length 3 or more (so three dice is the breakpoint between "okay" and "pretty good"). Otherwise, it's pretty standard for a modern mainstream system: stats, figured stats, skill ratings; roll your dice, add to a skill rating, compare to target number; combat happens in rounds; damage accumulates until it reaches a certain level and then you die; insanity accumulates until you go mad and become and NPC; etc. Not innovative, but it seems workable.